This invention pertains generally to the field of integrated optical components for use in fiber optic communications systems, and more particularly it relates to photonic switching. Specifically, the invention is a two-input/two-output integrated optical changeover switch with a very high extinction ratio.
Optical 2.times.2 changeover switches are known in the art and serve as key components for building photonic systems such as one-sided switching networks, two sided switching networks and Benes networks. Currently, the most favorable technology for fabricating optical changeover switches is integrated optics. Many integrated optical devices have been used, or suggested to be used, as 2.times.2 changeover switches. Some examples are directional couplers, reverse delta-beta couplers, cross-switches and BOA-couplers. It is well known in the art that the performance of photonic systems using switches made from these conventional integrated optical devices is limited by the accumulated loss and crosstalk. Only simple systems can be built currently. However, recent progress in optical amplifier technology has demonstrated that optical amplifier gain can compensate for this optical loss. If the use of optical amplifiers in optical systems proves practical, the remaining limiting factor for building more sophisticated optical systems is crosstalk.
It is obvious that optical system crosstalk can be reduced by using optical switches with higher extinction ratios. However, the routine fabrication of conventional integrated optical switches with very high extinction ratios still remains a problem area. Extremely tight control of the fabrication process is required.